Although adverse effects of in utero cocaine exposure upon the infant's size at birth and neurobehavioral function in the first few weeks of life have been shown, little is known about the implications of in utero cocaine exposures for these infants' later development. This five year longitudinal study employs a prospective single-bind cohort design to evaluate the potential multi-dimensional effects of in utero cocaine exposure upon the infant's health, growth, neurodevelopmental functioning and socioaffective development in the first two years of life. From a population of largely minority inner city women delivering at Boston City Hospital, a cohort of 150 neonates with in utero cocaine exposure will be identified by positive maternal or neonatal urine assay for cocaine metabolites in the perinatal period. Cocaine exposed infants will be matched to 150 non-exposed infants for mother's ethnicity, parity and mode of payment for medical care. Infants will undergo EEG, ultrasound, cry and growth and Brazelton assessments shortly following birth. Exposed and non- exposed infants will be enrolled in a primary care program at Boston City Hospital and research assessments linked to primary care visits to maximize compliance. Neurodevelopmental and socioaffective outcomes will be measured 4, 6, 12 and 24 months using the Movement Assessment of Infants, Bayley Scales of Infants Development, the Sequenced Inventory of Communication Development, observations of free play and face to face interaction, and the Ainsworth Strange Situation. To assess the role of postnatal environmental factors in influencing the outcomes, HOME assessments will be performed at 5, 11 and 23 months and mothers interviewed at 6, 12, 18 and 24 months regarding frequency/ quantity, mode, and cost of illicit drug use, alcohol use, stress, depression and social support. EMIT urine assays will be obtained at the time of enrollment and at the four follow-up interviews to substantiate mothers' illicit drug use. Multivariate analysis techniques, controlling potential confounders, will be used to compare exposed and nonexposed infants on outcomes of interest and to assess the role of mediating factors, such as the extent of the infant's neuro-physiologic dysfunction at birth and the quality of maternal caretaking, that may enhance or further compromise the outcomes of these infants. This information will permit the evolution of informed strategies of intervention for thousands of cocaine exposed infants and their mothers nationwide.